full marks science terms 2

10

CBSE

TERM-2

SCIENCE

(As per the latest CBSE Syllabus)

Jasvinder Kaur Randhawa M Sc, B Ed

MIT’s Vishwashanti Gurukul, Pune

FULL MARKS PVT LTD

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Full Marks Science-10 has been thoroughly revised and updated as per the latest

CBSE Syllabus. Apart from the other changes the book includes, Value-Based Questions, Test Your Skills and many more to strengthen the confidence of

the students in such a way that they can master the subject with easy method The book has been divided into two volumes separately for SA-I and SA-II. The chapters have been serialised as they figure in the Termwise Syllabus. It provides the students an opportunity to have a clear and concentrated view of the Task they have to learn during two different Terms.

The book is, thus, an up-to-date, dependable and learner-friendly resource. The support website www.fullmarks.org is an added benefit for the users where one

can get much more and also an opportunity to share one’s academic complexities.

Note from the Publisher

FIRST TERM Marks: 90

S. No. Units Marks

1. I. Chemical Substances—Nature and Behaviour 33

2. II. World of Living 21

3. IV. Effects of Current 29

4. V. Natural Resources 07

Total 90

THEME: MATERIALS (30 Periods)

Unit I: Chemical Substances—Nature and Behaviour

Chemical reactions: Chemical equation, Balanced chemical equation, implications of a balanced

chemical equation, types of chemical reactions : combination, decomposition, displacement, double displacement, precipitation, neutralization, oxidation and reduction.

Acids, bases and salts: Their definitions in terms of furnishing of H+ _{and OH}– _{ions, General}

properties, examples and uses, concept of pH scale (Definition relating to logarithm not required), importance of pH in everyday life; preparation and uses of Sodium Hydroxide, Bleaching powder, Baking soda, Washing soda and Plaster of Paris.

Metals and non metals: Properties of metals and non-metals; Reactivity series; Formation and

properties of ionic compounds; Basic metallurgical processes; Corrosion and its prevention.

THEME: THE WORLD OF THE LIVING (20 Periods)

Unit II: World of Living

Life Processes: “Living Being”. Basic concept of nutrition, respiration, transport and excretion

in plants and animals.

Control and Co-ordination in Animals and Plants: Tropic movements in plants; Introduction of

plant hormones; Control and co-ordination in animals: Nervous system; Voluntary, involuntary and reflex action; Chemical co-ordination: animal hormones.

THEME: HOW THINGS WORK (32 Periods)

Unit IV: Effects of Current

Electric current, potential difference and electric current. Ohm’s law; Resistance, Resistivity, Factors on which the resistance of a conductor depends. Series combination of resistors, parallel combination of resistors and its applications in daily life. Heating effect of electric current and its applications in daily life. Electric power, Interrelation between P, V, I and R.

Magnetic effects of current: Magnetic field, field lines, field due to a current carrying conductor,

field due to current carrying coil or solenoid; Force on current carrying conductor, Fleming’s Left Hand Rule. Electromagnetic induction. Induced potential difference, Induced current. Fleming’s Right Hand Rule, Direct current. Alternating current: frequency of AC. Advantage of AC over DC. Domestic electric circuits.

THEME: NATURAL RESOURCES (08 Periods) Unit V: Natural Resources

Sources of energy: Different forms of energy, conventional and non-conventional sources of energy:

fossil fuels, solar energy; biogas; wind, water and tidal energy; Nuclear energy. Renewable versus non-renewable sources of energy.

SECOND TERM Marks: 90

S. No. Units Marks

1. I. Chemical Substances—Nature and Behaviour 23

2. II. World of Living 30

3. III. Natural Phenomena 29

4. V. Natural Resources 08

Total 90

THEME: MATERIALS (25 Periods)

Unit I: Chemical Substances—Nature and Behaviour

Carbon compounds: Covalent bonding in carbon compounds. Versatile nature of carbon.

Homologous series. Nomenclature of carbon compounds containing functional groups (halogens, alcohol, ketones, aldehydes, alkanes and alkynes), difference between saturated hydrocarbons and unsaturated hydrocarbons. Chemical properties of carbon compounds (combustion, oxidation, addition and substitution reaction). Ethanol and Ethanoic acid (only properties and uses), soaps and detergents.

Periodic classification of elements: Need for classification, Modern periodic table, gradation in

properties, valency, atomic number, metallic and non-metallic properties.

THEME: THE WORLD OF THE LIVING (30 Periods)

Unit II: World of Living

Reproduction: Reproduction in animals and plants (asexual and sexual) reproductive health—

need and methods of family planning. Safe sex vs HIV/AIDS. Child bearing and women’s health.

Heredity and Evolution: Heredity; Mendel’s contribution- Laws for inheritance of traits: Sex

determination: brief introduction; Basic concepts of evolution.

THEME: NATURAL PHENOMENA (23 Periods)

Unit III: Natural Phenomena

Reflection of light by curved surfaces; Images formed by spherical mirrors, centre of curvature, principal axis, principal focus, focal length, mirror formula (Derivation not required), magnification. Refraction; Laws of refraction, refractive index.

Refraction of light by spherical lens, Image formed by spherical lenses; Lens formula (Derivation not required); Magnification. Power of a lens; Functioning of a lens in human eye, defects of vision and their corrections, applications of spherical mirrors and lenses.

Refraction of light through a prism, dispersion of light, scattering of light, applications in daily life.

THEME: NATURAL RESOURCES (12 Periods)

Unit V: Natural Resources Conservation of natural resources.

Management of natural resources. Conservation and judicious use of natural resources. Forest and wild life. Coal and Petroleum conservation. Examples of People’s participation for conservation of natural resources.

Regional environment: Big dams: advantages and limitations; alternatives, if any. Water harvesting.

Our environment: Eco-system, Environmental problems, Ozone depletion, waste production and

their solutions. Biodegradable and non-biodegradable substances.

QUESTION PAPER DESIGN

Time: 3 hours Max. Marks: 90

S.

No. Typology of Questions

Learning outcomes and testing competencies Very Short Answer (VSA) Short Answer-I (SA-I) Short Answer-II (SA-II) Long Answer

(LA) MarksTotal Weightage% 1 Mark 2 Marks 3 Marks 5 Marks

1. REMEMBERING

(Knowledge

based-Simple recall questions, to know specific facts, terms, concepts, principles, or theories, identify, define, or recite, information) • Reasoning • Analytical Skills • Critical Thinking Skills etc. 3 — 1 1 11 15% 2. UNDERSTANDING ( Comprehension-to be familiar with meaning and to understand conceptually, interpret, compare, contrast, explain, paraphrase, or interpret information) — 1 4 1 19 25% 3. APPLICATION

(Use abstract information in concrete situation, to apply knowledge to new situations. Use given content to interpret a situation, provide an example, or solve a problem)

— — 4 1 17 23%

4. HIGH ORDER THINKING SKILLS (Analysis & Synthesis- Classify,

compare, contrast or differentiate between different pieces of information. Organize and/or integrate unique pieces of information from a variety of sources)

— 2 — 1 9 12%

5. EVALUATION AND MULTI-DISCIPLINARY

(Appraise, judge, and/or justify the value or worth of a decision or outcome, or to predict outcomes based on values)

— — 3 2 19 25%

Total (Theory Based Questions) 3×1=3 3×2=6 12×3=36 6×5=30 75(24) 100% Practical Based Questions (PBQs) 9×1=9 3×2=6* — — 15(12)

TOTAL 12×1=12 6×2=12 12×3=36 6×5=30 90(36) * One question of 3 marks will be included to assess the values inherent in the texts.

CONTENTS

4. Carbon and its Compounds ... 9 5. Periodic Classification of Elements ... 48 II. World of Living

8. How do Organisms Reproduce? ... 79 9. Heredity and Evolution ... 109 III. Natural Phenomena

10. Light—Reflection and Refraction ... 132 11. Human Eye and Colourful World ... 174 V. Natural Resources

15. Our Environment ... 202 16. Management of Natural Resources ... 218

SYLLABUS

CLASS X

Second Term Marks: 90

Units Marks

I. Chemical Substances—Nature and Behaviour 23

II. World of Living 30

III. Natural Phenomena 29

V. Natural Resources 08

TOTAL 90

DIVISION OF CHAPTERS

Sl. Nos. and Names of Chapters in NCERT Book

4. C

C

5. p

C

e

8. H

o

r

?

9. H

e

10. l

—r

r

11. H

e

C

w

16. m

n

r

Carbon and its Compounds

4

Facts that Matter

Carbon Symbol – C

Electronic configuration – 2, 4 Valency – 4 (tetravalency)

Occurrence in nature → Earth’s crust →0.02% in the form of minerals like carbonates, coal, petroleum.

In atmosphere – 0.03% of carbon dioxide (gaseous form).

Carbon forms covalent bonding and covalent compounds which do not conduct electricity. A covalent bond is formed by mutual sharing of electrons. This mutual sharing of electrons occurs in such a way that each of the combining atom acquires the stable electronic configuration of the nearest noble gas. A single bond is formed when each of the two combining atoms share 1 electron each, a double bond is formed when atoms contribute 2 electrons each and triple bond is formed when each atom contributes 3 electrons.

Allotropy ⎯⎯→ Some elements exist in two or more different forms. This phenomenon is known as allotropy.

SYLLABUS

Covalent bonding in carbon compounds. Versatile nature of carbon, Homologous series, Nomenclature of carbon compounds containing functional groups (halogens, alcohol, ketones, aldehydes, alkanes and alkynes), Difference between saturated hydrocarbons and unsaturated hydrocarbons, Chemical properties of carbon compounds (combustion, oxidation, addition and substitution reaction), Ethanol and Ethanoic acid (only properties and uses), Soaps and detergents.

Allotropes of Carbon ⎯⎯→ Carbon has 3 allotropes: diamond, graphite and fullerenes. In diamond carbon atoms are bonded together in tetrahedral lattice arrangement. In graphite carbon atoms are bonded together in sheets of hexagonal lattice.

In fullerenes, carbon atoms are bonded together in spherical, tubular, or ellipsoidal forms. Organic compounds: The tetravalency of carbon gives a possibility of large number of compounds. Earlier it was thought carbon compounds can be extracted from organisms only. Hence carbon compounds are also called organic compounds.

NCERT IN-TEXT ACTIVITIES SOLVED

Activity 4.1

List of ten things used or consumed daily

Things Metals Glass/Clay Other materials

Fan Aluminium/Iron — —

Bed — — Wood (C)

Toothbrush Plastic, nylon (C)

Spoon Stainless steel

Tumbler Glass

Clothes Cotton (C)

Pencil Graphite Wood (C)

Pen Steel Plastic (C)

Books Paper-obtained from wood (C)

Bread Wheat (C)

(C) ⎯⎯→ indicates carbon Most substances contain carbon in it.

Activity 4.2

Calculate the difference in the formulae and molecular masses for (a) CH₃OH and C₂H₅OH (b) C₂H₅OH and C₃H₇OH, and (c) C₃H₇OH and C₄H₉OH.

(a) CH₃OH _{differ by CH} 2 C₂H₅OH Mass CH₃OH C₂H₅OH 12 + 1 × 3 + 16 + 1 = 32 u (12 × 2) + (1 × 5) + 16 + 1 = 46 u Difference → 46 – 32 = 14 u (b) C₂H₅OH _{differ by CH} 2 C3H7OH Mass C₂H₅OH C₃H₇OH (12 × 2 ) + (1 × 5) + 16 + 1 = 46 u (12 × 3) + (1 × 7) + 16 + 1 = 60 u Difference → 60 – 46 = 14 u ⎫ ⎬ ⎭ ⎫ ⎬ ⎭

(c) C₃H₇OH _{differ by CH} 2 C4H9OH Mass C3H7OH C4H9OH 60 u (12 × 4) + (1 × 9) + 16 + 1 = 74 u Difference →74 – 60 =14 u

All 3 groups given above show a similarity→Two consecutive members differ by CH2 group and mass 14 u.

Homologous Series

Chloro alkane Alcohol Aldehyde Ketone Carboxylic acid

CH₃Cl CH₃—OH HCHO CH₃—&

O

C—CH₃ HCOOH

C₂H₅Cl C₂H₅—OH CH₃CHO C₂H₅—&

O

C—CH₃ CH₃COOH

C₃H₇Cl C₃H₇—OH C₂H₅CHO C₃H₇—&

O

C—CH₃ C₂H₅COOH

C₄H₉Cl C₄H₉—OH C₃H₇CHO C₄H₉—&

O

C—CH₃ C₃H₇COOH Activity 4.3

Heating of different carbon compounds, observing the flame and smoke.

Carbon Compounds Nature of flame Deposits on Metal

Camphor Smoky flame Carbon deposits on metal

Alcohol Non-sooty flame No carbon

Acetone Non-sooty flame No carbon

Naphthalene Smoky flame Carbon deposits on metal Alcohol and acetone burns with non-sooty flame—complete combustion takes place. Camphor, naphthalene burns with sooty flame—incomplete combustion takes place. Activity 4.4

Bunsen burner is used to study the different types of flame by adjusting the holes at the base of the burner.

(i) When hole is closed—Yellow, sooty flame is formed, black deposits of carbon is obtained on spoon when placed above the flame.

(ii) When the hole is open—Blue flame is formed, no black deposits of carbon is obtained on spoon when placed above the flame.

Activity 4.5

Take 3 ml of ethanol in a test tube and warm it gently in a water bath.

Add 5% solution of alkaline potassium permanganate drop by drop to this solution.

⎫ ⎬ ⎭

• The colour of KMnO₄ slowly fades and disappears completely. When excess of KMnO₄ is added, the colour will not disappear as alcohol gets oxidised to form carboxylic acid.

In this case ethanol gets oxidised to form ethanoic acid due to KMnO₄ but the excess KMnO₄ will not decolourise.

Activity 4.6

Take a test tube with ethanol in it and drop a small piece of sodium metal in it. The reaction takes place and hydrogen gas is evolved.

To test the presence of hydrogen gas, bring a burning match stick near the mouth of the test tube, it will burn with pop sound.

2Na + 2CH₃CH₂OH ⎯→ 2CH3CH2ONa + H2 Sodium Ethanol Sodium ethoxide Hydrogen

Activity 4.7

pH test and litmus test of acetic acid and dilute hydrochloric acid and litmus test.

Litmus test pH

dil. CH3COOH Blue litmus turns red 5 – 6 less acidic dil. HCl Blue litmus turns red 2 – 3 more acidic Activity 4.8

Take 1 ml ethanol and 1 ml glacial acetic acid along with a few drops of concentrated sulphuric acid in a test tube.

Warm in a water-bath for at least five minutes. Pour into a beaker containing 20–50 ml of water.

• Pleasant fruity smelling compound is obtained called ester. Such a chemical reaction is called esterification.

CH3—COOH + CH3—CH2OH 4 2 Conc. H SO dehydrating agent ⎯⎯⎯⎯⎯⎯→ _{CH3COOC2H5 + H2O}

Ethanoic acid Ethanol Ester Water

Activity 4.9

Take a spatula full of sodium carbonate in a test tube and add 2 ml of dilute ethanoic acid. Pass the gas produced through freshly prepared lime water. Repeat the above procedure with sodium hydrogen carbonate.

• Following reactions take place

2CH₃COOH + Na₂CO₃ ⎯⎯→2CH₃COONa + H₂O + CO₂ CH3COOH + NaHCO3 ⎯⎯→ CH3COONa + H2O + CO2

The brisk effervescence of CO₂ gas is obtained which when pass through lime water turns it milky.

Activity 4.10

Take about 10 ml of water each in two test tubes. Add a drop of oil (cooking oil) to both the test tubes and label them as A and B. To test tube B, add a few drops of soap solution. Now, shake both the test tubes vigorously for the same period of time.

Shake the test tubes and then leave it undisturbed for some time. This shows how soap cleans dirt. Dirt is oily in nature. Hydrophobic part of soap bonds with dirt and dirty clothes are cleaned.

Activity 4.11

Take about 10 ml of distilled water and 10 ml of hard water in separate test tubes.

Add a couple of drops of soap solution to both. Shake the test tubes vigorously for an equal period of time.

The test tube which contains distilled water produces foam and the test tube with hard water forms curdy white precipitate.

Activity 4.12

Take two test tubes with 10 ml of hard water in each. Add five drops of soap solution to one and five drops of detergent solution to the other. Shake both the test tubes for the same period.

• Solution of hard water and soap forms curdy white precipitate. The hard water and detergent forms foam.

NCERT IN-TEXT QUESTIONS SOLVED

Q1. What would be the electron dot structure of carbon dioxide which has the formula CO₂?

Ans. The electron dot structure of CO₂ is

Q2. What would be the electron dot structure of a molecule of sulphur which is made up of

eight atoms of sulphur?

Q3. How many structural isomers can you draw for pentane? Ans. Three structural isomers can be drawn from pentane.

Pentane : C5H12

n-Pentane Iso-Pentane

Neo-Pentane

Q4. What are the two properties of carbon which lead to the huge number of carbon

compounds we see around us?

Ans. Carbon form large number of compounds due to the following properties:

(a) Catenation → Carbon shows the property of catenation that is the ability to form bonds with other carbon atoms forming long chains both branched and unbranched chains, and even rings.

(b) Tetravalency → Carbon has valency 4, it is capable of bonding with 4 other carbon atoms or atoms of other non-covalent elements, giving rise to compounds with specific properties depending on the elements present in the compound.

(c) Isomerism → Carbon compounds show the property of isomerism that is compounds having same molecular formula but different structural formula. Q5. What would be the formula and electron dot structure of cyclopentane?

Ans. The formula of cyclopentane is C5H10. The electron dot structure is

C C C C C H H H H H H H H H H

Q6. Draw the structures for the following compounds.

(i) Ethanoic acid (ii) Bromopentane

(iii) Butanone (iv) Hexanal

Are structural isomers possible for bromopentane?

Ans. (i) Ethanoic acid CH₃COOH

(ii) Bromopentane C₅H₁₁Br

(iii) Butanone C₂H₅COCH₃

(iv) Hexanal [C₅H₁₁CHO] Isomers of Bromopentane H C C C C C H H H Br H H H H H H H 3-Bromopentane

Q7. How would you name the following compounds:

(i) CH₃—CH₂—Br (ii)

(iii)

Ans. (i) Bromo ethane (ii) Methanal (iii) Hex-1-yne

Q8. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?

Ans. Conversion of ethanol to ethanoic acid is an oxidation reaction because oxygen is added to ethanol to convert it to ethanoic acid.

CH₃ – CH₂OH ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯4 →

2 2 7

Alk.KMnO +heat

(or)Acidified K Cr O +heat CH3COOH

Ethanol Ethanoic acid

In the above reaction alk. KMnO₄/acidified K₂Cr₂O₇ add oxygen to ethanol hence they are called oxidising agent.

Q9. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of

ethyne and air is not used?

Ans. If air is used, incomplete combustion will take place giving a sooty flame and less heat is produced. When pure oxygen is used ethyne burns completely producing large amount of heat and blue flame. This heat is sufficient for a metal to melt and welding is done.

Q10. How would you distinguish experimentally between an alcohol and a carboxylic acid? Ans. (a) Acid test: Reaction with carbonates/hydrogen carbonates.

Take samples of alcohol and carboxylic acid in 2 test tubes, and add sodium carbonate or sodium bicarbonate solution to each. The compound which will produce brisk effervescence of CO₂ gas will be acid.

(b) Alcohol test: Take small amount of ethanol and ethanoic acid in test tube A and B. Add 5% solution of alkaline potassium permanganate drop by drop to this solution and warm the test tube.

The colour of potassium permanganate will disappear in test tube containing alcohol. Q11. What are oxidising agents?

Ans. The compounds which add oxygen to other substance are known as oxidising agent. For example, alkaline potassium permanganate solution and acidified potassium dichromate, both can convert alcohol into carboxylic acid, i.e., ethanoic acid.

CH₃ – CH₂OH 4

7 2 2

Alk. KMnO +heat AcidifiedK Cr O +heat

⎯⎯⎯⎯⎯⎯⎯⎯⎯→ _CH

3COOH + H2O

Q12. Would you be able to check if water is hard by using detergent? Ans. No, because detergent forms lather in both, hard and soft water.

Q13. People use variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the

clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?

Ans. Soap lowers the surface tension of water. The long chain non-ionic hydrocarbon group in soap gets attached to the oil or grease droplets and loosens them from the fibres of cloth along with the dirt. However this loosening is insufficient to remove the grease with dirt completely. Hence the clothes are agitated to remove the grease droplets completely.

QUESTIONS FROM NCERT TEXTBOOK

Q1. Ethane, with the molecular formula C2H6 has

(a) 6 covalent bonds. (b) 7 covalent bonds.

(c) 8 covalent bonds. (d) 9 covalent bonds.

Ans. (b) 7 covalent bonds.

Q2. Butanone is a four-carbon compound with the functional group

(a) carboxylic acid. (b) aldehyde.

(c) ketone. (d) alcohol.

Ans. (d) ketone.

Q3. While cooking, if the bottom of the vessel is getting blackened on the outside, it means

that

(a) the food is not cooked completely. (b) the fuel is not burning completely.

(c) the fuel is wet. (d) the fuel is burning completely.

Ans. (b) The fuel is not burning completely.

Q4. Explain the nature of the covalent bond using the bond formation in CH3Cl.

Ans. Bond formation in CH3Cl

Carbon forms single covalent bond by sharing one electron pair with three hydrogen atoms and one chlorine atom. Chlorine being more electronegative adds polar nature to C—Cl bond.

Q5. Draw the electron dot structure for

(a) ethanoic acid. (b) H₂S.

Ans. The electron dot structure are as follows: (a) Ethanoic acid – CH₃COOH

(b) H2S

(c) Propanone (d) F2

Q6. What is an homologous series? Explain with an example.

Ans. It is a group of members of same class of organic compound having similar chemical properties, they have same general formula.

They have same functional group, when arranged in the ascending order of molecular mass they differ by 14 a.m.u. or —CH2 group.

Example: Alkane General formula — CnH2n+2 Methane CH₄

–CH₂

Ethane C2H6

Propane C₃H₈

Butane C4H10

Q7. How can ethanol and ethanoic acid be differentiated on the basis of their physical and

chemical properties?

Ans. Physical Properties

Ethanoic acid Ethanol

1. Pungent smell Pleasant smell

2. Melting point 290 K M.P. is 156 K

3. Boiling point 391 K B.P. is 351 K

Chemical Properties

Ethanoic acid Ethanol

1. Ethanoic acid + Sodium No CO₂ gas produced. bicarbonate gives CO2 gas.

2. On addition of alk. KMnO₄ the On addition of alk. KMnO₄ colour does not disappear. the colour disappear.

⎫ ⎬ ⎭

Q8. Why does micelle formation take place when soap is added to water? Will a micelle be

formed in other solvents such as ethanol also?

Ans. Soap molecules have two ends with different properties. One end is hydrophilic, which dissolves in water and other end is hydrophobic, it dissolves in hydrocarbons. When soap is added to water, the ionic end of soap will form a unique orientation and keep the hydrocarbon tail away from it.

The cluster of molecules is formed in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. Hence, micelle formation takes place.

Soap is soluble in ethanol hence the micelle formation will not take place.

Q9. Why are carbon and its compounds used as fuels for most applications?

Ans. Carbon and its compounds undergo combustion to produce heat, the amount of heat released can be handled and used so they are used as fuels for most applications. Q10. Explain the formation of scum when hard water is treated with soap.

Ans. Hard water contains salts of calcium and magnesium. When soap molecule comes in contact with these salts it forms a curdy white precipitate (compound insoluble in water) called scum.

Soap + Hard water ⎯→ scum

Q11. What change will you observe if you test soap with litmus paper (red and blue)? Ans. Soap is alkaline in nature, hence it will turn red litmus into blue, blue litmus will

remain blue.

Q12. What is hydrogenation? What is its industrial application?

Ans. When unsaturated hydrocarbons (double/triple bond) are reacted with hydrogen in presence of a catalyst like nickel, the hydrogen gets added across the double/triple bond and converts the unsaturated hydrocarbon into saturated hydrocarbon. Such reaction is called addition reaction or hydrogenation.

Example :

Industrial use: It is used to convert vegetable oil into vanaspati ghee. Vegetable oil + H₂ ⎯⎯⎯⎯_473KNi → Vanaspati ghee

Q13. Which of the following hydrocarbons undergo addition reactions?

C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄.

Ans. Addition reaction takes place in unsaturated hydrocarbons.

Hence C₃H₆ and C₂H₂ are unsaturated hydrocarbons and will show addition reaction. Q14. Give a test that can be used to differentiate chemically between butter and cooking oil.

Ans. Butter is saturated compound and oil is unsaturated compound. Test

alk. potassium permanganate + Unsaturated → Pink colour disappear. (Pink colour) hydrocarbon

Therefore, when we add oil to a test tube containing alkaline potassium permanganate solution, the pink colour of the solution disappear. Colour of alkaline potassium permanganate will not disappear in the test tube containing butter.

Q15. Explain the mechanism of cleaning action of soaps.

Ans. Soap molecule has two ends, the charged end that gets attracted towards water is called hydrophilic and the long carbon chain that repels water is called hydrophobic end. When soap is dissolved in water, the carbon chain i.e., hydrophobic end gets attracted towards the oil, dirt and grease. The hydrophilic end stays away from this. The micelle formation takes place.

The tail entangles dirt, oil or grease, if required the agitation is done. Lot of rinsing is a done with water so that water molecules attract charged (Na+) end and carries the soap molecules with dirt attached to it and clean the clothes, utensils, etc.

MORE QUESTIONS SOLVED

I. MULTIPLE CHOICE QUESTIONS

1. The isomeric pair is

(a) ethane and propane (b) propane and butane

2. The structural formula of ethyl ethanoate

(a) (b)

(c) (d)

3. Which of the following is used to oxidise ethanol to ethanoic acid? (a) Alkaline KMnO₄ (b) Conc. H₂SO₄

(c) Acidified K₂Cr₂O₇ (d) All of above

4. The compound which gives a brisk effervescence with sodium metal and not with sodium hydrogen carbonate is

(a) ethanol (b) ethanoic acid

(c) both ethanoic acid and ethanol (d) none of these

5. Identify the product formed when methane reacts with chlorine in the presence of sunlight is

(a) C₂Cl₆ (b) CH₃Cl

(c) CHCl₄ (d) None of these

6. Which is denatured spirit?

(a) ethanol only (b) ethanol and methanol (50%) (c) ethanol and methanol (5%) (d) methanol only

7. Drinking alcohol and driving may cause serious accidents. To discourage this, police randomly test drivers for alcohol using a breath analyser. The breath analyser works because

(a) Alcohol makes the breath dry and the machine registers moisture (b) Alcohol makes the breath hotter which changes the machine reading (c) Alcohol causes more saliva which the machine checks.

(d) Alcohol in the breath cause a chemical change registered by the machine. 8. Tertiary butane gets oxidised with oxidising agents like alkaline KMNO₄ to

(a) Isobutane (b) Ter-butyl alcohol

(c) Secondary-propyl alcohol (d) All of above

9. According to IUPAC system, the correct name of the organic compound is

(a) 2-bromobutanoic acid (b) 2-bromobutysis acid

10. The substance not responsible for the hardness of water is

(a) sodium nitrate (b) calcium hydrogen carbonate (c) calcium carbonate (d) magnesium carbonate 11. The by product of soap is

(a) isoprene (b) glycerol

(c) butene (d) ethylene glycol

12. Covalent compounds

(a) have high melting and boiling points (b) are mostly soluble in water

(c) are formed between atoms of metals and non-metals

(d) are formed by the sharing of electrons in the bonding atoms. 13. The heteroatoms present is

CH₃ – O – CH₂ – CH₂ (Br)

(a) oxygen (b) carbon

(c) hydrogen (d) bromine

14. Vinegar is a solution of

(a) 30% – 40% acetic acid in alcohol (b) 5% – 8% acetic acid in alcohol (c) 5% – 8% acetic acid in water (d) 15% – 20% acetic acid in water 15. Which of the following can be used for the denaturation of ethyl alcohol?

(a) Methyl alcohol (b) Pyridines (c) Copper sulphate (d) All of above 16. Soaps are formed by saponification of

(a) alcohols (b) glycosides

(c) simple esters (d) carboxylic acids 17. The correct electron dot structure of a water molecule is

(a) (b)

(c) (d)

18. Acetic acid was added to a liquid X kept in a test tube. A colourless and odourless gas Y was evolved. The gas was passed through lime water which turned milky. It was concluded that:

(a) Liquid X is sodium hydroxide and the gas Y is CO₂ (b) Liquid X is sodium carbonate and the gas Y is CO₂ (c) Liquid X is sodium acetates and the gas Y is CO₂ (d) Liquid X is sodium chloride and the gas Y is SO₂.

19. For gas welding used for welding broken pieces of iron, we normally use a mixture of (a) Ethane and oxygen (b) Ethene and oxygen

20. Identify the compound that undergoes bromination reaction: (a) –C–C– | | | | (b) | | | –C–C–C– | | | (c) | | – C – C – C C – | | (d) All of above

21. Bromine reacts with saturated hydrocarbon at room temperature in the (a) absence of sunlight (b) presence of water

(c) presence of sunlight (d) presence of hydrochloric acid 22. The number of single and double bonds present in benzenes are

(a) 9 and 6 (b) 9 and 3

(c) 12 and 3 (d) 12 and 6

23. Identify the correct way of numbering an organic compound (according to IUPAC)

(a) (b)

(c) (d)

24. Identify the functional group present in the following compound

(a) aldehyde (b) bromine

(c) carboxylic (d) both bromine and carboxylic group 25. The upper and lower homologue of C₂H₅OH are respectively

(a) methyl alcohol and butyl alcohol (b) ethyl alcohol and propyl alcohol (c) butyl alcohol and propyl alcohol (d) propyl alcohol and methyl alcohol 26. Which is not true about homologous series?

(a) They have same general formula. (b) They differ from other by CH₃ group. (c) They have same functional group. (d) They have same chemical properties.

27. Name the following aromatic compound

(a) toluene (b) aniline

(c) phenol (d) furan

28. Ethanoic acid was added to sodium carbonate solution and the gas evolved was tested with a burning splinter. The following four observations were reported. Identify the correct observation.

(a) The gas burns with pop sound and the flame gets extinguished (b) The gas does not burn but the splinter burns with pop sound (c) The flame extinguishes and the gas does not burn

(d) The gas burns with a blue flame and the splinter burns brightly 29. Which of the following is not a straight chain?

(a) ₃ − ₂− ₂ − ₂ 3 | CH CH CH CH CH (b) CH₃ – CH₂ – CH₂ – CH₂ – CH₃ (c) − − − ₃ | 3 2 2 2 CH H C H C CH CH _(d) 3 2 3 3 CH \ CH CH CH / H C − −

30. The general formula for alkanes is C_nH_2n+1–CHO. The value of ‘n’ for the first member.

(a) 1 (b) 0 (c) 0.5 (d) 1.1

31. An organic compound ‘X’ has the molecular formula C₃H₆O₂. It has a pleasant smell but does not turn blue limus red. It has structural formula

(a) − − || 3 H C C OH O (b) || − − 3 3 O CH C O CH

Answers

II. VERY SHORT ANSWER TYPE QUESTIONS (1 Mark)

Q1. What is a hydrocarbon?

Ans. It is a compound of hydrogen and carbon.

Q2. Give different forms in which carbon occurs in nature.

Ans. Carbon occurs in free form e.g., graphite and diamond in combined form like carbon dioxide, carbonates, etc.

In earth’s crust–0.02% and in atmosphere–0.03%. Q3. Name two types of hydrocarbon.

Ans. Hydrocarbon – Saturated and unsaturated. Q4. What are covalent bonds?

Ans. Bond which are formed by sharing of a pair of electrons between two atoms is called covalent bonds.

Q5. What is catenation?

Ans. Carbon has the unique ability to form bonds with the other atoms of carbon which gives rise to large molecules. This property of self linking is called catenation. Q6. Name two allotropes of carbon.

Ans. Two allotropes are – Crystalline and amorphous Crystalline form – Diamond and graphite. Amorphous form – Charcoal, coal, coke.

Q7. Why covalent compounds have low melting and boiling points?

Ans. As the bond is formed by sharing of electrons between two atoms. Intermolecular forces are small between the covalent compounds. These bonds break easily.

Q8. Define oxidising agents.

Ans. Some substances are capable of adding oxygen to others. These substances are known as oxidising agents.

Example: alkaline KMnO4 and acidified K2Cr2O7.

Q9. Give the reaction to show how alcohol is converted into carboxylic acid. Ans. CH₃ — CH₂OH 4

7 2 2

alk. KMnO + heat acidified K Cr O

⎯⎯⎯⎯⎯⎯⎯⎯→_CH3COOH

Q10. Identify the compound

Ans. Propyne.

Q11. Name the compound

Ans. Benzene, C₆H₆.

Q12. Give two properties of ethanol. Ans. (a) Liquid at room temperature

(b) Soluble in H₂O in all proportions

Q13. Give the formula for the functional group of aldehyde. Ans.

Q14. What are heteroatoms?

Ans. An element or group of elements which replaces one or more hydrogen (H) atoms from hydrocarbon, such that valency of carbon remains satisfied.

Example: CH₄ ⎯→ CH3 – OH Hence, —OH is a heteroatom. Q15. Define catalyst.

Ans. Catalyst are substances that cause a reaction with a change in rate of reaction, without itself undergoing any change.

Example: Micelle acts as a catalyst to convert unsaturated hydrocarbon into saturated hydrocarbon.

Q16. Complete the following reaction:

Q17. Give the full form of IUPAC.

Ans. IUPAC → International Union of Pure and Applied Chemistry. Q18. How can esters be converted into soap?

Ans. By saponification reaction, by adding/reacting ester with NaOH. Q19. How can we convert CH₃CH₂OH into C₂H₄ ?

Ans. By adding conc. sulphuric acid into it which acts as dehydrating agent and removes water from it.

CH3– CH2OH ⎯⎯⎯⎯H SOConc._{2 4}→ CH2==CH2 + H2O

Q20. Give two properties of ionic compounds.

Ans. (i) High melting point and high boiling point. (ii) Can conduct electricity.

Q21. What is the melting point of acetic acid? Ans. M.P. = 290 K.

Q22. Name the given compound .

Ans. 2-Butanone.

Q23. How can you convert ethene into ethane?

Ans. By adding hydrogen to ethene in the presence of a catalyst. Q24. What is addition reaction? Give one example.

Ans. The process of adding hydrogen across the double bonds of unsaturated hydrocarbons is called addition reaction.

For example : H2C==CH2 + H2 ⎯⎯⎯⎯CatalystNi →H3C—CH3

Ethene Ethane

Q25. What is esterification reaction?

Ans. The reaction in which alcohol reacts with carboxylic acid to produce a new compound called ester is called esterification.

Q26. Give two uses of methane gas.

Ans. (i) It is used as a fuel (ii) It is the major component of biogas and CNG. Q27. What is isomerism?

Ans. A property in which a compound can exist in different structural formula but its molecular formula remains the same.

Q28. Why can’t we test hard water with detergents?

Ans. Detergents form lather with both hard and soft water hence we cannot distinguish between them.

Q29. What is hydrophilic?

Ans. The substance showing attraction towards water is called hydrophilic. Q30. Name the second member of alkyne series.

Ans. Propyne

Q31. Give the names of the functional group

(i) —CHO (ii) —C==O

Ans. (i) —CHO → Aldehyde (ii) → Ketone Q32. The structural formula of an ester is

H C C C O H H H H C H H C H O H H

Name the alcohol and the acid from which it would have been formed.

Ans. Alcohol is C2H5OH ethanol

Acid is H₃C—H₂C—COOH propanoic acid.

Q33. Give the IUPAC name of acetic acid and propyl alcohol. Ans. Acetic acid – Ethanoic acid

Propyl alcohol – Propanol

Q34. What will happen to the litmus solution in carboxylic acid? Ans. Red litmus remains the same but blue litmus changes to red. Q35. Give the electron dot structure of CH3Cl and C2H2.

Ans. CH3Cl

C₂H₂

Q36. Draw the electron dot structure of N2 and NH3.

Ans. N₂ ⎯→ N xx Nx x x x x x x _x NH3 ⎯→

Q37. Why do soaps form scum when added to hard water?

Ans. Hard water contains carbonate and sulphate salts of magnesium or sodium ions which react with the soap molecule to form a compound which is insoluble in water. Hence soaps form scum with hard water.

Q38. What happens when ethanol burns in air?

Ans. Ethanol burns to form carbon dioxide and water.

Q39. Give the IUPAC name and write the functional group present in vinegar. Ans. Vinegar IUPAC name is acetic acid CH3COOH

Functional group –COOH

Q40. A compound has a molecular formula C2H6O. It is used as a fuel. Name the compound

and name its functional group.

Ans. C₂H₆O is an alcohol, i.e. ethanol C₂H₅OH Functional group is —OH.

III. SHORT ANSWER TYPE QUESTIONS (2 or 3 Marks)

Q1. What is the reactive site in the given hydrocarbon? Write its name. H₃C—CH₂—CH==CH—CH₃

Ans. The reactive site is at a place where double bond is present. Name of the compound is 2-pentene.

Q2. What is the difference in the number of carbon and hydrogen atoms between two

successive members of a homologous series? Also give the difference in their atomic masses.

Ans. The difference is of 1 carbon and two hydrogen atoms i.e., —CH2 and mass difference is 14 a.m.u.

Q3. Name the peculiar/specific chemical property exclusive in case of saturated hydrocarbons

and unsaturated hydrocarbons.

Ans. Saturated hydrocarbons show substitution reaction in which hydrogen atom gets substituted by other elements or atoms. Unsaturated hydrocarbons show addition reaction, in which hydrogen atom gets added across the double bond or triple bond of the compound.

Q4. Why acetic acid is called glacial acetic acid?

Ans. Acetic acid has very low melting point i.e. 290 K, hence it freezes during winters in cold countries. So it is called glacial acetic acid.

Q5. Why does carbon forms large number of compounds?

Ans. Carbon forms large number of compounds because of tetravalency and catenation property.

Tetravalency – Carbon has valency 4, to attain noble gas configuration carbon share its valence electrons with other elements like hydrogen, chlorine, etc.

Catenation – Carbon also shows the property of self-linking in which it forms long, branched or cyclic chains to form large number of compounds.

Q6. Write the structural formula for bromopentane and ethanoic acid.

Ans. Bromopentane (C5H12Br) Ethanoic acid (CH3COOH)

H C C C C C Br H H H H H H H H H H H C C OH H H O

Q7. How does ethanoic acid react with carbonates and hydrogen carbonates? Show it with

the equation.

Ans. Ethanoic acid reacts with carbonates and hydrocarbonates to form salt, CO2 and H2O. The salt formed is sodium acetate.

2CH₃COOH + Na₂CO₃ ⎯→ 2CH3COONa + H2O + CO2 CH₃COOH + NaHCO₃ ⎯→ CH3COONa + H2O + CO2

Q8. Draw the structures of two isomers of butane. Ans. Butane C₄H₁₀ (i) H C C C H H H H C H H H H H n-butane (ii) H C C C H H C H H H H H H H iso-butane

Q9. A student burns a hydrocarbon in air and obtains sooty flame. Give two reasons for this

observation.

Ans. Sooty flame could be obtained due to

(i) Incomplete combustion of saturated hydrocarbons. (ii) Combustion of unsaturated hydrocarbon.

Q10. Differentiate between saturated and unsaturated hydrocarbons. Give one example for

each.

Ans. Saturated hydrocarbon Unsaturated hydrocarbon

1. It consist of single bond in Double or triple bond in carbon–carbon

carbon–carbon. is present.

2. It burns with blue flame. It burns with sooty flame. 3. Show substitution reaction Show addition reaction.

4. Less reactive More reactive

Eg. CH₄ Methane E.g. H₂C=CH₂ Ethene

Q11. Write the general formula for each of the following hydrocarbons and give one example

for each.

(i) Alkene (ii) Alkyne

Ans. (i) Alkene CnH2n e.g., C2H4 ethene (ii) Alkyne CnH2n–2 e.g., C2H2 ethyne

Q12. Name the functional groups of the following:

(a) CH3—Cl (b) CH3— & O C–OH (c) CH₃— & O C – CH₃ (d) C₂H₅OH

Ans. (a) Chloro (Halogen) (b) Carboxylic acid

(c) Ketone (d) Alcohol

Q13. Explain substitution reaction with example.

Ans. The reaction of saturated hydrocarbon with chlorine in which each hydrogen atom slowly gets substituted with chlorine atom is called substitution reaction.

CH₄ + Cl₂ ⎯⎯→ CH₃Cl + HCl Methane Chlorine Methyl Hydrochloric

chloride acid

Q14. Diamond and graphite show different physical properties although they are made up of

carbon and shows same chemical properties. What is this property called?

Ans. This property is allotropy.

The physical properties are different because the carbon-carbon bonding in both the cases varies. In diamond one carbon atom is bonded with four other carbon atoms with strong covalent bond so it is hard, while in case of graphite each carbon forms two strong bonds with other two carbon atoms and one weak bond is formed with third carbon atom and forms hexagonal rings which slide over each other, so it is soft.

Q15. What is denatured alcohol?

Ans. When ethanol is mixed with methanol or some poisonous substances such as copper sulphate, pyridine which makes it unfit for drinking such alcohol is called denatured alcohol.

Q16. What is esterification and give its uses?

Ans. It is the reaction in which esters are formed by reacting carboxylic acid with alcohol in the presence of concentrated sulphuric acid.

Carboxylic acid + alcohol⎯⎯→ Ester + water C2H5OH + CH3COOH⎯⎯→ CH3COOC2H5 + H2O

Ethanol Ethanoic acid Ester

Uses:(i) It is used as flavour in ice-cream and sweets. (ii) It is a sweet smelling substance.

Q17. Give difference between soap and detergent.

Ans. Soap Detergent

1. Soaps are the sodium salts of the Detergents are generally ammonium or long chain carboxylic acids. sulphonate salts of long chains carboxylic

acid.

2. Soaps are not suitable for washing with Detergents do not form insoluble scum with hard water as it forms insoluble scum. hard water.

3. Soaps are prepared from fats or Detergents are not prepared from fats or

vegetable oils. vegetable oils.

4. Biodegradable Non-biodegradable.

Q18. Differentiate between ethanol and ethanoic acid on basis of the following test: (i) Blue litmus test (ii) Reaction with sodium bicarbonate (iii) Sodium metal test Ans. Test Ethanol Ethanoic acid

(i) Blue litmus → turns red turns red test

(ii) NaHCO₃ C₂H₅OH + NaHCO₃ ⎯→ CH₃COOH + NaHCO₃ ⎯→ C₂H₅ONa + H₂O + CO₂ CH₃COONa + H₂O + CO₂ (iii) Na test 2C2H5OH + 2Na ⎯→ 2CH3COOH + 2Na ⎯→

2C2H5ONa + H2 2CH3COONa + H2

Q19. Giving chemical equations of the reactions write what happens when (i) Ethanol is heated with excess of concentrated sulphuric acid at 443 K. (ii) Ethanoic acid reacts with ethanol in presence of an acid.

(iii) Ester with molecular formula CH3COOC2H5 reacts with sodium hydroxide.

Ans. (i) C₂H₅OH ⎯⎯⎯⎯⎯→_{Conc. H SO}heat_{2 4} H₂C==CH₂ + H₂O

ethanol ethene

(ii) C2H5OH + CH3COOH ⎯⎯⎯acid→ CH3COOC2H5 + H2O Ethanol Ethanoic acid Ester

(iii) CH3COOC2H5 + NaOH ⎯→ C2H5OH +CH3COOH CH3COOH + NaOH ⎯→ CH3COONa + H2O

Q20. How can you obtain the following from pure ethanol:

(i) Ethene (ii) Ethanoic acid (iii) Ester?

Ans. (i) Ethene: Ethanol when heated with excess of concentrated sulphuric acid will form ethene.

C₂H₅OH ⎯⎯⎯⎯⎯→_{Conc. H SO}heat_{2 4} H₂C==CH₂ + H₂O Ethene

(ii) Ethanoic acid: On oxidation of ethanol with an oxidising agent like alkaline KMnO₄ or acidified K₂Cr₂O₇, ethanoic acid is formed.

CH3—CH2OH ⎯⎯⎯⎯⎯⎯⎯₂ 4_{2 7}→ alk. KMnO

acidified K Cr O CH3COOH

ethanoic acid

(iii) Ester: To get esters, ethanol is reacted with any carboxylic acid. Example: C2H5OH + CH3COOH ⎯⎯⎯acid→ CH3COOC2H5 + H2O Ethanol Ethanoic acid Ester

The above reaction takes place in the presence of an acid. Q21. Write the chemical equations for the following reactions:

(i) Conversion of oils into fats (ii) Oxidation of ethanol (iii) Ethanoic acid with sodium hydroxide.

Ans. (i)

(ii) Oxidation of ethanol

C2H5OH ⎯⎯⎯⎯⎯→alk. KMnO4 CH3COOH

Ethanol Ethanoic acid

(iii) CH₃COOH + NaOH ⎯→ CH3COONa + H2O

Ethanoic acid Sodium Sodium hydroxide acetate

Q22. An organic compound ‘X’ which is also called antifree mixture has the molecular formula

C2H6O ‘X’ on oxidation gives a compound ‘Y’ which gives effervescence with a baking soda

solution. What can X and Y be? Write their structural formula.

Ans. X is ethanol, (C₂H₅OH) Y is ethanoic acid (CH₃COOH) Structural formula Ethanol _{H C C OH} H H H H Ethanoic acid H C C OH H H O

Q23. Write the structures of isomers of hexane. Ans. (i) H C C C H H H H C H H H H H C H H C H H n-Hexane

(ii) H C C C H H C H H H C H H H H C H H H H 2-Methyl pentane (iii) H C C C H H H H C C H H H H H H C H H H 3-Methyl pentane (iv) H C C C H H H H C CH3 H H H CH3 2, 3-Dimethyl butane (v) H C3 C CH2 CH3 CH3 CH3 2, 2-Dimethyl butane

Q24. Complete and balance the following equations: (a) CH3CH2OH + O2 ⎯→

(b) Na + CH3CH2OH ⎯→

(c) CH3–CH2OH

Ans. (a) 2CH3CH2OH + 6O2 ⎯⎯→ 4CO2 + 6H2O + heat + light (b) 2Na + 2CH₃CH₂OH _⎯⎯→ 2CH₃CH₂ONa + H₂

(c) CH3–CH2OH ⎯⎯⎯⎯⎯→conc. H SO2 4 H2C==CH2 + H2O

Q25. Give two uses of ethanol and one harmful effect of it.

Ans. Ethanol is a good solvent so it is used in making medicines such as tincture iodine, cough syrups and many tonics. Ethanol is also used in making alcoholic drinks. Harmful effects: Intake of small amount of ethanol leads to drunkenness. Intake of even small amount of ethanol can be lethal. Long-term use or consumption can lead to severe health problems.

Q26. (a) Why are covalent compounds generally poor conductors of electricity? (b) Name the following compound:

(c) Name the gases evolved when ethanoic acid is added to sodium carbonate. How would

you prove the presence of this gas?

Ans. (a) Covalent compound do not form ions. (b) Propanone

(c) Ethanoic acid reacts with sodium carbonate to produce carbon dioxide gas. To prove the presence of this gas allow it to pass through lime water (freshly prepared). It turns lime water milky.

Equation

2CH₃COOH + 2Na₂CO₃ ⎯→ 2CH3COONa + H2O + CO2 Test for the gas evolved → Ca(OH)2 + CO2 ⎯→ CaCO3 + H2O

Lime water Milky ppt. Q27. (a) Complete the following equations:

(i) CH₃CH₂OH ⎯⎯⎯⎯⎯→Conc. H SO2 4

Heat

(ii) CH₃COOH + NaHCO_{3 ⎯⎯→}

(iii) CH4 + Cl2 ⎯⎯⎯⎯Sunlight→

(b) Write the name of the following:

(i) CH3CH2COOH (ii) CH3CH2Br

(c) Draw the electron dot structure of ethene(C2H4). (CBSE 2008 C)

Ans. (a) (i) CH₃CH₂OH ⎯⎯⎯⎯⎯→Conc. H SO2 4

Heat H2C==CH2 + H2O

ethene

(ii) CH₃COOH + NaHCO_{3 ⎯⎯→} CH₃COONa + H₂O + CO₂

Sodium ethanoate

(iii) CH4 + Cl2⎯⎯⎯⎯Sunlight→ CH3Cl + HCl

Chloromethane

(b) (i)Propanoic acid (ii) Bromoethane (c) Electron dot structure of ethene

Q28. (a) Name the compound CH3CH2OH and identify its functional group.

(b) Give a chemical test to distinguish between ethanol and ethanoic acid.

(c) Name the product formed when an organic acid reacts with an alcohol in presence of an

acid catalyst. What is the name assigned to this type of reaction? (AI CBSE 2008 C)

Ans. (a) CH₃CH₂OH – Ethanol

(b) Take two test tubes, add ethanol and ethanoic acid in test tube A and B respectively. Add sodium carbonate/sodium hydrogen carbonate solution in both the test tubes, the test tube which will produce brisk effervescence of CO2 gas will contain ethanoic acid. Ethanol do not evolve CO₂ gas when reacted with Na₂CO₃/ NaHCO3.

(c) When an organic acid reacts with an alcohol in presence of an acid as catalyst, it produces fruity smelling compound called ester. Such a reaction is called esterification.

Example: CH₃COOH + C₂H₅OH _{⎯⎯⎯⎯⎯→}Conc. H SO2 4 CH₃COOC₂H₅ + H₂O

Q29. (a) Name the compound CH₃COOH and identify its functional group.

(b) Give a chemical test to identify this compound.

(c) Name the gas evolved when this compound acts on solid sodium carbonate. How

would you identify this gas? (AI CBSE 2008 C) Ans. (a) Ethanoic acid, functional group is—COOH (Caboxylic/group)

(b) Take few drops of ethanoic acid in a test tube and add sodium hydrogen carbonate solution to it. Brisk effervescence of CO₂ gas is formed.

(c) CO₂ gas is evolved. To identify the gas, pass it through freshly prepared lime-water, it turns milky due to the formation of milky white precipitate of CaCO3. Ca(OH)2 + CO2 ⎯⎯→ CaCO3 + H2O

White ppt.

Q30. (a) Give a chemical test to distinguish between saturated and unsaturated hydrocarbons. (b) (i) Name the products formed when ethanol burns in air.

(ii) What two forms of energy are liberated on burning alcohol?

(c) Why is the reaction between methane and chlorine considered a substitution reaction? (AI CBSE 2008 C) Ans. (a) On adding bromine water, the unsaturated hydrocarbon decolourises the bromine

water but the saturated hydrocarbon will not decolourise bromine water. (b) (i) Ethanol burns in air to produce carbon dioxide and water.

C₂H₅OH + 3O₂ ⎯⎯→ 3CO₂ + 3H₂O + heat

(ii) Two forms of energy obtained are heat energy and light energy.

(c) When methane reacts with chlorine, the hydrogen atom of methane is replaced by chlorine atom step by step and hence it is termed as substitution reaction. CH4 + Cl2 ⎯⎯→ CH3Cl + HCl

Q31. Give reason for the following observations:

(b) Air holes of a gas burner have to be adjusted when the heated vessels get blackened by

the flame.

(c) Use of synthetic detergents causes pollution of water. (CBSE 2009) Ans. (a) Carbon forms large number of compounds due to its property of catenation, i.e. self linking. They form isomeric compounds i.e. compounds with same molecular formula but different structural formula.

(b) The vessels blacken due to deposits of black carbon particles on it which is caused due to incomplete combustion of fuel. Air holes are adjusted so that air enters through the holes and helps in complete combustion of the fuel.

(c) Synthetic detergent is non-biodegradable, it remains in the water thereby causing water pollution.

Q32. (a) What is a ‘homologous series’ of substances?

(b) In an organic compound, which parts largely determine its physical and chemical

properties?

(c) Write a chemical equation to represent the reaction of ethanol with acidified solution

of potassium dichromate. (AI CBSE 2009) Ans. (a) Homologous series is a series of organic compounds having same general formula, all members of the compounds show same chemical properties and slight gradation in physical properties.

(b) Functional group.

(c) CH3CH2OH + 2[O] ⎯⎯⎯⎯⎯⎯_{2 2 7}→ acidified

K Cr O CH3COOH + H2O

Ethanol Ethanoic acid

Q33. (a) What is vinegar?

(b) Describe with a chemical equation, what happens when sodium hydrogen carbonate

reacts with ethanoic acid. (AI CBSE 2009) Ans. (a) The 5% – 10% aqueous solution of acetic acid is called vinegar.

(b) CH3COOH + NaHCO3 ⎯⎯→ CH3COONa + H2O + CO2

Acetic acid Sodium acetate

Ethanoic acid reacts with sodium bicarbonate to produce brisk effervescence of CO2 gas and sodium acetate.

Q34. (a) Write the names of the functional groups in:

(i) (ii)

(b) Describe a chemical test to distinguish between ethanol and ethanoic acid.

(c) Write a chemical equation to represent what happens when hydrogen gas is passed

through an unsaturated hydrocarbons in the presence of nickel as a catalyst.

Ans. (a) (i) Ketone (ii) Aldehyde

(b) On adding Na₂CO₃/NaHCO₃, the test tube containing ethanoic acid produces brisk effervescence of CO2 gas. Alcohol will not show any reaction.

CH3COOH + NaHCO3 ⎯→ CH3COONa + CO2 + H2O C2H5OH + NaHCO3 ⎯→ No reaction

(c) H₂C==CH₂ + H₂ ⎯⎯⎯⎯_CatalystNi → H₃C — CH₃

Ethene Ethane

Unsaturated Saturated

hydrocarbon Hydrocarbon

IV. LONG ANSWER TYPE QUESTIONS (5 Marks)

Q1. An organic compound ‘A’ is widely used as a preservative in pickles and has a molecular

formula C2H4O2. This compound reacts with ethanol to form a sweet smelling

compound ‘B’.

(a) Identify the compound ‘A’.

(b) Write the chemical equation for its reaction with ethanol to form compound ‘B’. (c) How can we get compound ‘A’ and ‘B’?

(d) Which gas is obtained when compound ‘A’ reacts with washing soda? Give the equation. (e) Write an equation to obtain ‘A’ back from ‘B’.

Ans.(a) ‘A’ is CH₃COOH acetic acid.

(b) CH₃COOH + C₂H₅OH _⎯⎯→ CH₃COOC₂H₅ + H₂O

(c) We can get compound A back by the process of saponification. (d) A + washing soda _⎯⎯→ CO₂ gas is produced

2CH3COOH + Na2CO3 ⎯⎯→ 2CH3COONa + H2O + CO2 (e) Saponification

CH3COOC2H5 ⎯⎯⎯→NaOH C2H5OH + CH3COONa

Q2. Identify the compound A, B, C, D, and E in the following reaction: (a) CH3CH2OH CH3COOH (b) CH₃CH₂OH + CH₃COOH ⎯⎯⎯→_{H SO}conc. 4 2 + H2O (c) B + NaOH → C₂H₅OH + C (d) D + Na2CO3 → CH3COONa + E + H2O (e) E + Ca(OH)2 → F + H2O white ppt.

Ans. (a) A = Alkaline KMnO₄ or acidified K₂Cr₂O₇ (b) B = CH₃COOC₂H₅

(c) C = CH3COONa

(d) D = CH₃COOH; E = CO₂ (e) E = CO2; F = CaCO3

Q3. What are soaps? Explain the mechanism of the cleansing action of soaps? Soaps form scum

with hard water. Explain why? How this problem is overcome by use of detergents?

Ans. Soaps are sodium salts of fatty acids. It is biodegradable and shows cleansing action by removing dirt.

Mechanism of cleansing action: Soap has molecules with tadpole like structure. Carbon chain

ion Na+

Its head is made of Na+ ion which is hydrophilic and long tail is made up of hydrocarbon chain which is hydrophobic, it attracts the dirt and removes it. When soap is added to water it forms micelles and helps in removing the dirt which sticks to the carbon chain. On rinsing the cloth with water it helps in removing the dirt, as Na+ is hydrophilic. It attracts water and carries its tail entangled with dirt and flows away with water.

Scum formation: Soaps form scum with hard water because hard water has salts of calcium and magnesium which react with soap to form insoluble compound called scum.

In case of detergents, the salts present in hard water does not react with the molecules of detergent to form insoluble compound called scum, but the molecules of detergent remain as it is and helps in the cleansing action.

Q4. (a) What do you mean by allotropy? (b) What is isomerism?

(c) Give one example of homologus series, give two properties of it. (d) What is the full form of IUPAC?

Ans. (a) Allotropy: It is the property of an element in which element show same chemical properties but different physical properties, due to difference in the bonding of atoms.

Example: Diamond and graphite are having same chemical properties but they look/appear to be physically different as the bonding in both differs.

C C _C C C Diamond C Graphite C C C C C C C C C C C

(b) Isomerism: It is the property of hydrocarbons which show same molecular formula but exhibits different structural formulae.

Example: Butane C H₃ C C CH₃ H H H H n-butane H3C CH CH3 CH₃ iso-butane

Both of them show different properties.

(c) Homologous series: When the members of a hydrocarbon family obey same general formula they are said to be in homologous series. When the members are arranged in increasing order of their molecular masses:

Example: Alkane – C_nH_2n+2 CH₄ — Methane C₂H₆ — Ethane C₃H₈ — Propane C₄H₁₀ — Butane Properties:

(i) The difference between two consecutive members of homologous series is of —CH2 and mass 14 a.m.u.

(ii) They all show same chemical properties and slight gradation in their physical properties.

(d) IUPAC: International Union of Pure and Applied Chemistry. Q5. (a) What are hydrocarbons?

(b) Give difference between saturated and unsaturated hydrocarbons. (c) Why does carbon form large number of compounds?

Ans. (a) Hydrocarbons – A compound of carbon and hydrogen.

(b) Saturated Unsaturated

1. C—C single bond C==C, C≡≡C double or triple bond.

2. Alkanes CnH2n+2 Alkenes CnH2n, and Alkynes CnH2n–2

3. Undergo substitution reaction Undergo addition reaction

4. Burns with blue flame Burns with sooty flame

(c) Carbon forms large number of compounds due to

(i) Catenation – Self linking property which leads to long straight chains, branched chains and cyclic chains.